The present invention relates to a new an improved construction of apparatus for welding together two profile or section rods, by means of resistance welding, especially for welding together two rails, which apparatus is of the type comprising clamping devices operatively associated with each of the profile rods and having contact electrodes for the infeed of the welding current and means in order to displace the clamping devices relative to one another in the direction of the profile rods, to thereby exert a pressure force at the weld or welding joint.
It is known for such machines to construct the clamping devices to be displaceable and also rotatable to a limited degree in a plane which is at right angles to the lengthwise extent of the profile or section rods to be interconnected, in order to be able to mutually align the profile or contour of both profile or section rods prior to welding.
Since, however, such profile or section rods, as a general rule, constitute rolled profiles, and thus, automatically are associated with comparatively large manufacturing tolerances, and furthermore, since it is practically impossible to avoid that the end faces of the profile or section rods to be welded together are not exactly at right angles or perpendicular to their lengthwise axis, during the actual welding operation and also during the application of the pressure force at the welding joint there occurs so-called "distortions" or "displacements" of both profile rods in relation to one another. Under the term "distortion" or "displacement" as used in this context there should be understood the phenomena occurring, under such circumstances, during the welding operation in terms of both abutting or impact surfaces participating in the welding operation mutually shifting under simultaneous plastic deformation and deviation from the profile axis of both end regions of the profile or section rods which directly adjoin the welding joint.
When this phenomenon occurs, apart from the de-burring of the welding joint which is required in any case, there is either necessitated a complicated post-machining operation at the region of the welding joint, or, however, the welding joint itself must again be disconnected and a new welding operation performed.